Tenacious edge retention

[jackknifeh]

nevermind.

Jack

:)

[Blerv]

Hey Cliff,

You mentioned that a coarse sharpening of a low carbon/carbide neutral steel could provide ample performance at the penalty of steel degradation. Would you say that the vanadium carbide/high hardness steels have an advantage over the more "simple" carbon neutral steels in that they wear slower and thus maintain more optimal edge geometry?

No intent to twist words or win. I still think angle and sharpening skill reigns supreme over product snobbery. Just trying to look at this from another perspective for those who NEED the latest and greatest in wear resistant alloys. As you mentioned these more expensive steels don't appear to "wear out" as fast. With the average flat-grind, low carbon, low hardness steel it seems angle alone will make a noticeable difference eventually.An optimist would say the latter is "better" on that basis while the economist may say "worse" depending on the price tag. :)

[shimage]

Here is what you were looking for, Jack.

(...) the answer is no, you would not notice a difference (...)

Note that if you disagree, or if you think he's just nuts, then you need to understand the rest of what he wrote (which involves a great deal of qualification) to understand why he gave the answer he did. You don't need to be a metallurgist or a physicist/chemist to understand any of it, but a familiarity with experimental technique and statistics/data analysis is useful.

That said, I won't vouch for the veracity of his more specific claims, because I don't really feel like reading the literature on the subject. This aversion to research seems to be true for pretty much everyone here that isn't Cliff, which makes it more of a lecture than a discussion. Still, I found it interesting, and what he says is certainly consistent with my limited experience.

[jackknifeh]

Here is what you were looking for, Jack.



Note that if you disagree, or if you think he's just nuts, then you need to understand the rest of what he wrote (which involves a great deal of qualification) to understand why he gave the answer he did. You don't need to be a metallurgist or a physicist/chemist to understand any of it, but a familiarity with experimental technique and statistics/data analysis is useful.

That said, I won't vouch for the veracity of his more specific claims, because I don't really feel like reading the literature on the subject. This aversion to research seems to be true for pretty much everyone here that isn't Cliff, which makes it more of a lecture than a discussion. Still, I found it interesting, and what he says is certainly consistent with my limited experience.

I understand what you are saying and concede a vast lack of knowledge about metal, steel and most of what Cliff talks about. You could fill up a bunch of books with the information I don't know. Wait, I think someone already did that. :) However most of what Cliff says (lately) disagrees with the experiences I get with knife blades. I DO see a difference in 8Cr13MoV and S30v or M4 or ZDP-189 in edge retention. My angles are very close (30 - 36 deg.) on about all of my EDC knives and my sharpening skill is identical. Then I get Cliff's opinion which contradicts what I actually experience with my own two hands. In addition to that he explains his side of the discussion in ways that I just don't understand. This is all very cool for me. Maybe I am wrong for whatever reason. But I'll side with the results I see and can touch before I buy a bunch of knives with the blade steel that doesn't perform as well after it gets to my house. :)

No matter what the "truth" is, it is interesting. Here is another thing for Cliff. Just a suggestion. When someone wants a simple answer, just give it to them simply. I may miss a good point you make because it is hidden in writing I don't uderstand so I skim through it. My fault I know. I'm sure there are others who gain from your thorough explanations. But when put simply "you won't see a difference" I can get on with disagreeing with you. :D I will continue to pay attention to how my blades and edges perform out of plain interest. One area I haven't done much paying attention to is how long it takes and edge to get to VERY dull after it has a good working edge. Most of what I've paid attention to is an edge going from shaving sharp to the still good working edge. Once the good working edge is reached it seems to stop degrading near as fast as at the very sharp levels. Since I never use a knife for long periods of time any more I touch up my knives before they ever do get really dull, or even close to it.

Maybe ignorance is bliss.



Jack

[shimage]

However most of what Cliff says (lately) disagrees with the experiences I get with knife blades. I DO see a difference in 8Cr13MoV and S30v or M4 or ZDP-189 in edge retention.

That's fine, but this is why people that run experiments and analyze data for a living don't get along with normal people on forums. I used to spend a lot of time on audio forums, and you see these sorts of arguments with people talking past each other there too.

The problem is just that it is hard to do proper tests. You might think you are controlling for all the variables, but there is a very good chance that you are not. Really, at the end of the day, it doesn't matter what is "real" and what isn't. You pays your money and you takes your choice. If high end steels make you happy, then buy them :) No amount of data or theory is going to tell Cliff what makes you happy, but there are always going to be people like him who want to understand everything about their hobbies. That means quantifying and testing and trying to remove bias/systematic error. The last bit is always the toughest to deal with, and unless you have experience doing it, you are unlikely to get it right.

Maybe ignorance is bliss.

It often is. I sometimes wish I could forget things I've learned. Other times, I wish I could still remember them ...

[Cliff Stamp]

You mentioned that a coarse sharpening of a low carbon/carbide neutral steel could provide ample performance at the penalty of steel degradation. Would you say that the vanadium carbide/high hardness steels have an advantage over the more "simple" carbon neutral steels in that they wear slower and thus maintain more optimal edge geometry?

Yes, as hardness increases then abrasive wear resistance increases but it isn't as dramatic as people often claim. Here are some actual numbers on the abrasive wear of steels :

0.040 C : 50 HRC : 140 WF
0.090 C : 50 HRC : 130 WF

0.090 C : 60 HRC : 107 WF
0.090 C : 50 HRC : 130 WF

This compares the wear resistance (WF) of two steels (1040 and 1090) at the same hardness to see the extent of carbide volume and at two different hardness levels to see the extent of hardness. Note that even if you change the hardness of 1090 steel by 10 points, it increases wear resistance by about 20%. Now taking that into account what do you think 1-2 HRC points achieves. This is from a research paper on balls used in grinding copper ore so it is a pure abrasive wear test.

Now the alloy carbides however can increase raw abrasive wear tremendously because they are simply so much harder. The knoop hardness of pure cementite (iron carbide) is 1025, this is harder than full hard martensite. The hardness of vanadium carbide is 2660 hence why vanadium carbide is so dominant that steels can often end up ranking in wear resistance by vanadium percentages. However of course knives are not solid Vanadium carbide and edge retention isn't 100% wear even in wear based cutting as edges deform, fracture, etc. .

However yes, you will see better performance in for example F2 vs 1095 even in coarse edges and if you are willing to wear out a high wear knife then you will see better performance from it for abrasive slicing as you reduce the grit. If you want to take this to insane levels look at the review I did of the Mel Sorg knife in D2 where I compared the edge retention showing the influence of edge angle and extreme grit ranges on a custom knife were I was willing to sharpen it on a 100 grit abrasive which is so coarse you can see the teeth left in the edge and if you look at them even under slight magnification then even the teeth have teeth they are so large.

It is basically a serrated blade where the teeth are themselves serrated. Imagine a Spyderco edge where the teeth are ground on the inside with the Cold Steel mini-serrations. You have to first wear down the mini-teeth, and then the main teeth and then round out all the sharp edges left by the teeth fracturing. But again, when you do sharpen it - you are going to rip off an awful lot of steel.

The most extreme example of this I personally say was seeing my brother literally wear out a Basic #7 from Busse Combat in one year and part of it was using extremely coarse abrasives. Edge retention, speed of sharpening, cutting ability were all extremely high - but again in just one year he reduced a #7 to less than a #5.

There is a further complication though which is that when you get a knife made out of a knife class steel and it is ground so as to truly optimize the cutting ability you don't need to use extremely coarse abrasives to get very high cutting ability or edge retention. I rarely run x-coarse finishes aside from evaluations and instead get similar performance from much lower edge angles typically sharpening utility knives at 4-6 dps and chopping blades at 8-12 dps (depending on blade length, steel, exact wood type, etc.) .

However most of what Cliff says (lately) disagrees with the experiences I get with knife blades.

No it doesn't, in fact I have said explicitly I would expect you to see what you have described, what I have said is if you used proper methodology you would something very different. There is a reason these methods are used, if they were not necessary no one would do them as they take a tremendous amount of time and add significant complexity, however if you want conclusions to have even a decent degree of probability of truth you have to do them, otherwise you are just as well to roll dice and pick a conclusion.

When someone wants a simple answer, just give it to them simply.

The answer as noted was no. Other people read threads, both in the present and through future searches, etc. , they actually may be interested to know why the answer is no, if you are not then fine, don't read it.

Ever since I started doing commentaries on knives I constantly get asked at the start of any writeup could just rate the knives on a simple 1-5 scale so someone could know if the knife just good or bad without having to read anything.

My answer was always the same, if that is all you want then what I write isn't meant for you, there are lots of people who will jump at the chance to tell you if a knife is good or bad without any qualification just ask them, in fact I can even recommend them - no worries.

[setldown]

[Melektau]

Played with that bug for 20 minutes

[jinmo]

The answer as noted was no. Other people read threads, both in the present and through future searches, etc. , they actually may be interested to know why the answer is no, if you are not then fine, don't read it.

Ever since I started doing commentaries on knives I constantly get asked at the start of any writeup could just rate the knives on a simple 1-5 scale so someone could know if the knife just good or bad without having to read anything.

I enjoy the reasoning behind the answer. Granted, I know very little about metallurgy, but It shows me that it's more than opinion.